Pit pony work dust factor

by Mike

It has long been known that coal dust is one of the least harmful of all the dusts inhaled industrially. Since the practice of laying down stone dust in coal mines was adopted, however, a certain degree of uneasiness has been felt as to the possible effect of the stone dust on the collier’s lung.

With a somewhat dubious reassurance of the safety of coal dust (“least harmful dust inhaled industrially” is kind of like “least fattening cheesecake eaten voraciously”), F. Haynes of the University of Oxford begins an investigation(*) of the real menace to coal miners’ lungs: stone dust. To combat explosions, ground-up stone is applied inside mine shafts, diluting the highly combustible coal dust.

How much dust ends up in a miner’s lungs?

Does it get worse and worse over, say, a 20-year career?

How much lung damage does this produce?

To answer these questions, Haynes got mines to send him lung samples from various workers who either died on the job or were euthanized when they became unable to work. Not human miners — pit ponies, who were employed in large numbers before the advent of mechanized rail cars.

Coal miners and pit pony, 1913. Source: ancestry.com, which inserts this photo into random entries for people who happened to be coal miners.

To cut a long story short, the answers are:

Lots of dust.

No, it gets worse for about 2 years and then stays about the same.

Not much damage.

This does not apply to extremely dusty dusts, like those from fireclay or Bute clod(**).

And how did he measure dust, to answer 1 and 2?

Dust was quantified as “dust value”, graded from 0 (horse that did not live in a mine shaft) to 10.

To look for a relationship between quantity of dust and time spent in the mine, Haynes created the “work-dust factor”. This is simply a ratio of “dust value” to the number of years spent mining. If you have a dust value of 6 and have been working for 11 years, your work-dust factor is (6 / 11) or 0.545. If the dust keeps accumulating year after year, everyone’s work-dust factor should be similar. But as you can see from this table, as ponies keep working, their work-dust factor decreases.

Which means… as ponies keep working, their dust levels stay about the same. This becomes clear if we multiply the number of years by the “work-dust factor”. Which just gives us the original dust value that we started with. Which is about the same for all groups.

For combining two simple numbers into a confusing metric that was never used again by anyone, F. Haynes receives a special posthumous commendation in the fields of toxicology and biostatistics.